Find the next number in the sequence

5 12 24 36 ?

Name a key which is hardest to turn.

What does below science rebus mean?

Ag Ag Ag
Ag SPOON Ag
Ag Ag Ag

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

I inserted a coin in a bottle and closed its mouth with the help of a cork. Now, I was able to take the coin out from the bottle without taking out the cork or breaking the bottle. Can you tell me how I did it?

A man is found hanging dead from the ceiling of a room. The room’s dimensions are 15 x 15 x 15. The man is only 6ft tall and the rope was only 2ft long. There are no windows and only one door to the room. The door is bolted shut from the inside, and a puddle of water is under the man. How did he kill himself?

Name the three-letter word that can complete the below words:

A) L O _ _ _ E
B) E D U _ _ _ E
C) _ _ _ E R
D) _ _ _ T L E

I came first on earth but second on the heaven.
I also came twice in a week but found just once in a year.
I stay away from months but you can find me in February.

What am I?

Identify the hidden meaning behind this picture?